1. Field of the Invention
The present invention relates to a rotating power tool, and more particularly to a hand-held rotating power tool having a transmission assembly that guarantees normal operation and isolates any reactive force.
2. Description of Related Art
With reference to FIGS. 4 and 5, a hand-held rotating power tool (60) can be mounted on an articulated arm (70) and typically has two ends, a power unit (61) and a head (62). The power unit (61) is mounted in one end of the hand-held rotating power tool (60), supplies rotating power and has an armature. The head (62) is mounted rotatably in the other end of the rotating power tool (60) and allows a tip or a bit to be attached coaxially to the head (62). Generally, the head (62) is rotated by a transmission assembly mounted between the power unit (61) and the head (62). The transmission assembly comprises at least one planetary gear assembly. The planetary gear assembly comprises a sun gear, a planet carrier, two planetary gears and an annulus. The sun gear is connected coaxially to, protrudes from and is rotated by the armature. The planet carrier is mounted rotatably around the sun gear and is attached to and rotates the head (62). The planetary gears are mounted rotatably on the planet carrier opposite to each other and engage the sun gear. The annulus is stationary, is mounted around the planetary gears and has a toothed inner surface. The toothed inner surface engages the planetary gears and causes the planet carrier to rotate as the planetary gears are rotated by the sun gear.
However, the planetary gears are susceptible to becoming unstable during operation especially after extensive use and even modest gear wear and can be damaged easily. Furthermore, any longitudinal reactive force transmitted from the head (62) will be transmitted directly to the power unit (61). Therefore, frequent maintenance is needed to ensure normal operation of the hand-held rotating power tool (60), which is time consuming and inconvenient.
To overcome the shortcomings, the present invention provides a hand-held rotating power tool (60) to obviate or mitigate the aforementioned problems.